1. Field of the Invention
The present invention relates to an air-cooled plug part for an optical waveguide (LWL) which is particularly suited for the transmission of laser radiation.
2. Related Art
In transmitting laser radiation from a beam source to a processing station, a beam energy exists which typically lies in the range from a few milliwatt to several kilowatt. This energy is guided along an optical waveguide which generally has a diameter from 200 to 600 μm, in exceptional cases up to approximately 1.2 mm. An optical waveguide essentially consists of a core fiber (core) and a surrounding covering (cladding) which both are made of quartz glass. The cladding is adjoined by a silicone mass, and the outermost layer is often a plastic sheathing. The beam normally runs in the core fiber; if the radiation is not situated centrally in the core, an input of energy into the cladding will occur. The warming which is due to the high transmitted energy is counteracted by a cooling which acts at least along part of the length of the optical waveguide, in particular also on plug parts.
Cooled plug parts for optical waveguides are known. One possibility is to cool the optical waveguide and the plug part with water. For this purpose, water flows around the cladding at least on a part of its length and cools it intensively; the lost heat which occurs in normal use can be removed easily by the water owing to its high heat capacity.
With the transmission of laser radiation in the kilowatt range, however, the cladding may heat up excessively in some areas; the reasons for this are known to a professional, but they are of no relevance for the present invention and will not be explained in further detail. A typical maximum operating temperature which is still tolerated by the materials lies at approximately 300° C.
In practice it has been shown to be a problem that despite a water-assisted cooling the surface temperature of an optical waveguide may rise to more than 100° C., necessarily resulting in vapor bubbles. This is generally known in laser technology with water-cooled optics. In the case of a new contact with water, the quartz glass material sustains a shock in the zone which before was surrounded by the bubble; this often being a point of origin for the total destruction of the optical waveguide. A further problem is to maintain the leak-tightness of the water circulation against the background of thermal fluctuations. With such thermal fluctuations the differing coefficients of linear expansion of the materials (common matching glass/metal) are the reason for such problems in terms of leak-tightness.